The problem is that players who decree "no rush" are also the players who could reach late-game if they'd actually learn to play effectively - they're still going to get crushed in "no rush," particularly in a turn-based game where reflex is a non-issue, because they're still not actually good at playing effectively.
I had to respond to that!! Me was "unbeatable" in the Age of Empires LAN games.. one reason could be that other two opponents were my younger brother (He's younger by almost 10 years) and his friend..
PS: I also beat the "Ultima Weapon" in FF-X, and all the "Dark Aeons", too in the "International Version" of FF-X. (following the guide by Split Infinity). Just showing off some of my war medals there, 
Elemental MP would be good, there would be lots of tactics to explore, but the RULE should be, no early rushing. Say you cannot attack till your City is Level 5.
I don't want to play the game you're talking about. Not only that, but it also makes a good deal of the strategic depth go away; if people want to play like that, they don't need to have it hard-coded into the game, they have an spoken agreement before starting the game or use a mod.
you're right that someone is doing it wrong if you ever get to end game units.
Then the game needs to be fixed, or the players need to learn how to play. It's not a "rushing" problem, it's a mechanics problem. But while rush tactics can almost remove the "end-game" level from the game, "No-Rush" removes everything else. In a 4X, 3 of the Xs are actually happening mostly early-mid game.
Yep, that was what I was referring to, an agreement between players not to attack before a certain level of achievement/civilization has been met. Age of Empires was certainly not hard coded this way.
Early rush means the game could be over in five to fifteen minutes, when all you want to do is add a +1 to your "Win" stat. There was a post by FrogBoss about that, concerning the game Starcraft "Its not the game, its the players". Most players want to win in the first five minutes, they rush, if they win, game is over in 5 minutes. If they lose the initial rush, they quit. Either way the game is over in five minutes.
"Different strokes for different folks"